Literature references attest to the potential utility of nucleoside levels in the urine of cancer patients as "biological markers" for the diagnosis and monitoring of cancer. However, current methods of analysis are prone to interferences and lack the sensitivity necessary to quantate "rare" nucleosides. GCMS methods will, therefore, be used to quantate selected nucleosides in the urine of cancer patients by the stable isotope dilution and metastable ion monitoring techniques. In addition, mass spectrometry will be used to determine the structures of unknown nucleosides in cancer patient urine which may provide a better understanding of the biochemistry of cancer cells. Urine of cancer patients will be provided by my clinical collaborators and will include samples from persons with breast cancer, cancer of the colon and leukemia. Urine samples will be obtained upon diagnosis, during treatment and following therapy. Results will then be compared to determine the utility of urinary nucleosides as "biological markers" of cancer. Samples will be prepared and analyzed using methods developed in this laboratory. The methods have been tested using urine from normal persons and are now ready to be applied to clinical studies. The research described in this proposal has the potential of providing 1) a simple, noninvasive, rapid method for the diagnosis of cancer, 2) clinicians with a noninvasive and safe method for following the patients response to therapy, and 3) an indication of relapse by the patient.